Rock bit

ABSTRACT

The present invention provides a rock bit which enables a reduction in surface pressure from a well wall and which allows possible vibration to be suppressed. A first of the present invention provides a rock bit including a bit body with a journal portion, a cone portion configured to be rotatable with respect to the bit body, a bearing portion located between the cone portion and the journal portion, and a seal provided between the cone portion and the journal portion to seal the bearing portion, wherein the cone portion includes a gauge surface that contacts a side wall of a well, and a diamond composite material is preferably disposed extensively and smoothly on the gauge surface. In a second aspect of the present invention, a ring bit is provided at an outer peripheral portion of a bit body. Furthermore, a cone portion of a tri-cone bit includes no gauge tip or surface chip that contacts the side wall of the well but only cemented carbide tips that contact a bottom of the well.

INCORPORATION BY REFERENCE

The present application claims priority from Japanese application JP2010-013040 filed on Jan. 25, 2010, the content of which is hereby incorporated by reference into this application.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a rock bit.

(2) Description of Related Art

Tri-cone bits have recently been used as rock bits for well digging.

As shown in FIG. 10, a tri-cone bit includes a bit body 4 with a journal portion 2, a cone portion 6 configured to be rotatable with respect to the bit body 4, a bearing portion 8 located between the cone portion 6 and the journal portion 2, and a seal 10 provided between the cone portion 6 and the journal portion 2 to seal the bearing portion 8. A large number of cemented carbide tips 12 and 14 are embedded in the cone portion 6. The cemented carbide tips include cemented carbide tips 12 that contact the bottom of a well and gauge tips 14 that contact the side wall of the well. A gauge surface 16 that contacts the side wall of the well is formed inside each of the gauge tips 14 in the cone portion 6 (the gauge surface 16 is formed closer to the bit body 4 and the journal portion 2 than the gauge tip 14). A cemented carbide tip (gauge surface tip) 18 is also located on the gauge surface 16. The cemented carbide tip 18 located on the gauge surface 16 offers ultrahigh wear resistance but chips and crushes the well wall instead of grinding the well wall. As shown in FIG. 10, a ball bearing 8 a and a metal bearing 8 b are provided in the bearing portion 8.

U.S. Pat. No. 5,119,714 discloses an attempt to develop an ultrahigh-pressure technique in which natural or man-made diamond is used in order to enhance the wear resistance of the gauge tips and the gauge surface tips. In U.S. Pat. No. 4,940,099, polycrystalline diamond and cemented carbide tips are arranged on the gauge surface to enhance wear resistance. Neither U.S. Pat. No. 5,119,714 nor U.S. Pat. No. 4,940,099 does not describe that the tips are set to actively drill the well wall.

U.S. Pat. No. 5,346,026 discloses an attempt to maintain the gauge surface in order to keep the digging diameter of the well constant. U.S. Pat. No. 5,346,026 discloses an attempt to cut the well wall using a complicated combination of polycrystalline diamond (PDC or TSP), CBN, or the like with cemented carbide as well as an improved tip shape. These are measures for enhancing the wear resistance of the gauge surface and are not designed to suppress stress and vibration. Thus, the measures are not intended to protect the bearing portion 8 or the seal 10.

In connection with the seal 10, the study of the structure (U.S. Pat. No. 6,431,293 proposes an enhancing measure with a double seal) and the study of seal materials (for example, U.S. Pat. No. 5,456,327 proposes surface reformation of an O ring) are focused on.

A concern with the well digging rock bit is that muddy water may permeate through the seal 10 into the bearing portion 8 and act as an abrasive material to wear out the seal 10 and bearings 8 a and 8 b. The worn-out bearings 8 a and 8 b may distort the rotation of the cone portion 6 to cause a slip between the cemented carbide tips 12 and 14 and rocks. This may promote the wear. Moreover, a critical accident may occur; the cone portion 6 may slip off from the journal portion 2.

A pressure (F in FIG. 10) from the side wall of the well exerted on the bit during digging acts in a direction in which the cone portion 6 slips off (in the horizontal direction). All of the pressure from the well wall is received by the bearings 8 a and 8 b. In the rock bit, the cemented carbide tips (sometimes PCD tips) 18 or the like are located on the gauge surface 16 in order to prevent the gauge surface 16 from being worn. The cemented carbide tips 18 or the like are pressed into the rocks with the heads thereof exposed by about 1 mm to crush up the bedrock of the well wall in conjunction with the rotation of the cone portion 6. Forcibly crushing up the side wall causes the cone portion 6 to undergo a very high pressure from the well wall. All of the pressure F in the horizontal direction is received by the bearings 8 a and 8 b, which are thus worn and fatigued rapidly.

Furthermore, the bit body 4 is configured to support the cone portion 6 using the journal portion 2 formed at the long extending tip portion thereof. However, the bit body 4 is not so robust as it appears. An excessive force concentrates at the tip portion of the bit body 4. The pressure from the well wall causes the bit body 4 to be bent to distort the rotation of the cone portion 6, thus promoting the wear of the cemented carbide tips 14 and 16. The bit body 4 may infrequently be damaged.

In conjunction with the rotation of the cone portion 6, the protruding portion of the cemented carbide tips 18 embedded in the gauge surface 16 hits the well wall in a tangential direction. The bedrock is thus chipped and dug. At this time, the cone portion 6 generates intense vibration. The vibration occurs in the horizontal direction. Thus, cutting of sediment into the seal 10 is promoted. This results in wear-out of the seal 10, entry of sediment into the bearing portion 8, and wear-out of the bearings caused by the sediment acting as an abrasive material.

A main object of the present invention is to provide a rock bit which enables a reduction in surface pressure from the well wall and which allows possible vibration to be suppressed.

BRIEF SUMMARY OF THE INVENTION

A first of the present invention provides a rock bit including a bit body 4 with a journal portion 2, a cone portion 6 configured to be rotatable with respect to the bit body, a bearing portion 8 located between the cone portion and the journal portion, and a seal 10 provided between the cone portion and the journal portion to seal the bearing portion, wherein the cone portion includes a gauge surface 16 that contacts a side wall of a well, and a diamond composite material 20 is disposed on the gauge surface.

A composite wear resistant material disclosed in, for example, WO2006/080302 A1 (U.S. Pat. No. 7,637,981) the disclosure of which is incorporated by reference herein may be used as the composite material 20.

The diamond composite material may be disposed on the bit body, and preferably disposed extensively and smoothly on the bit body.

The rock bit may further include a gauge tip that contacts the side wall of the well. The diamond composite material may be disposed on a part of the gauge tip, and preferably disposed extensively and smoothly on a part of the gauge tip.

A second aspect of the present invention provides a rock bit including a tri-cone bit including a bit body 4 with a journal portion 2, a cone portion 6 configured to be rotatable with respect to the bit body, a bearing portion 8 located between the cone portion and the journal portion, and a seal 10 provided between the cone portion and the journal portion to seal the bearing portion, and a cylindrical ring portion 30 fixed to an outer periphery of the tri-cone bit and including a ring bit 32 located at a tip of the ring portion 30 so as contact a side wall of a well. The cone portion 6 of the tri-cone bit includes no gauge tip 14 that contacts the side wall of the well but only cemented carbide tips 12 that contact a bottom of the well.

The diamond composite material may be disposed on the ring bit, and preferably disposed extensively and smoothly on the ring bit.

The diamond composite material disclosed in, for example, WO2006/080302 A1 (U.S. Pat. No. 7,637,981) or Japanese Application No. 2009-142837 may be stacked on cemented carbide or iron-containing metal, and the stack may be disposed on the ring bit, and preferably disposed extensively and smoothly on the ring bit.

The first of the present invention provides a tip 20 of a gauge surface 16 with a grinding capability to allow the tip 20 to actively dig the well wall, thus releasing stress applied to the rock bit. Hence, burdens on the bearing portion 8 are reduced. The first of the present invention further allows horizontal vibration to be suppressed, thus reducing cutting of mud into the seal 10. Manufacturing the bit such that the burdens on the journal portion 2 and the seal 10 are reduced is an innovative new attempt.

When the diamond composite material is extensively disposed on the gauge surface 16 so as to eliminate protruding portions, the possible horizontal vibration of the cone portion 6 during rotation can be prevented.

As a result, cutting of sediment into the seal 10 is reduced, thus enhancing the seal 10.

According to the second aspect of the present invention, when the bit 32 of the cylindrical ring portion 30 is used to grind the outer peripheral portion of a digging pit and the normal tri-cone bit is used to dig the cylindrical rocks remaining in the central portion, no pressure from the well wall is applied to the gauge surface.

The outer peripheral portion of the bit rotates at high speed, and this meets a grinding condition for the ring bit. However, the central portion of the bit rotates at low speed. Thus, it is ideal to use a tri-cone bit to crush rocks during digging according to the conventional example. Furthermore, the cylindrical ring portion 30 prevents digging debris from entering the seal 10 and increases cooling efficiency to protect the seal from high temperature such as geothermal heat. In this case, the tri-cone bit need not serve to maintain the digging diameter (the ring bit instead fulfils this function), and there is no need to worry about the wear of the gauge surface or the like.

Moreover, no parallel pressure or vibration is applied to the seal, allowing the bit cone portion to rotate in the ideal environment.

Other objects, features and advantages of the invention will become apparent from the following description of the embodiments of the invention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a sectional view of a rock bit according to an embodiment of the present invention;

FIG. 2 is a front view of an example of a gauge surface of the rock bit on which a diamond composite material is disposed according to the embodiment of the present invention;

FIG. 3 is a front view of another example of the gauge surface of the rock bit on which the diamond composite material is disposed according to the embodiment of the present invention;

FIG. 4 is a front view of yet another example of the gauge surface of the rock bit on which the diamond composite material is disposed according to the embodiment of the present invention;

FIG. 5 is a front view of still another example of the gauge surface of the rock bit on which the diamond composite material is disposed according to the embodiment of the present invention;

FIG. 6 is a perspective view of an example of the diamond composite material disposed in a cemented carbide portion of the gauge surface of the rock bit according to the embodiment of the present invention;

FIG. 7 is a perspective view of another example of the diamond composite material disposed in the cemented carbide portion of the gauge surface of the rock bit according to the embodiment of the present invention;

FIG. 8 is a perspective view of yet another example of the diamond composite material disposed in the cemented carbide portion of the gauge surface of the rock bit according to the embodiment of the present invention;

FIG. 9 is a sectional view of a rock bit according to another embodiment of the present invention; and

FIG. 10 is a sectional view of a rock bit according to a conventional example.

DETAILED DESCRIPTION OF THE INVENTION Embodiment 1

An embodiment of a rock bit according to the present invention will be described with reference to FIG. 1. The rock bit includes a bit body 4 with a journal portion 2, a cone portion 6 configured to be rotatable with respect to the bit body 4, and a bearing portion 8 located between the cone portion 6 and the journal portion 2. The bearing portion 8 includes a ball bearing 8 a and a metal bearing 8 b. The rock bit further includes a seal 10 provided between the cone portion 6 and the journal portion 2 to seal the bearing portion 8. A large number of cemented carbide tips 12 and 14 are embedded in the cone portion 6. The cemented carbide tips include cemented carbide tips 12 that contact the bottom of a well and gauge tips 14 that contact the side wall of the well.

The cone portion 6 includes a gauge surface 16 that contacts the side wall of the well. Cemented carbide gauge surface tips 18 are provided on the gauge surface 16. A diamond composite material 20 is disposed on the gauge surface 16 and preferably disposed extensively and smoothly on the gauge surface 16.

FIGS. 2 to 5 show several examples in which the diamond composite material 20 is disposed on the gauge surface 16. FIG. 2 shows an example in which circular diamond composite materials 20 are disposed on the gauge surface 16. FIG. 3 shows an example in which parallelogrammatic diamond composite materials 20 are disposed on the gauge surface 16. FIG. 4 shows an example in which substantially trapezoidal diamond composite materials 20 are disposed on the gauge surface 16. FIG. 5 shows an example in which substantially triangular diamond composite materials 20 are disposed on the gauge surface 16.

FIGS. 6 to 8 show several examples in which the diamond composite material 20 is disposed on each of the cemented carbide tips, that is, the gauge surface tips 18 disposed on the gauge surface. FIG. 6 shows an example in which a plurality of linear diamond composite materials 20 are disposed on the gauge surface tip 18. FIG. 7 shows an example in which a plurality of circular diamond composite materials 20 are disposed on the gauge surface tip 18. FIG. 8 shows an example in which the diamond composite material 20 is disposed so as to cover the entire gauge surface tip 18.

A composite wear resistant member disclosed in WO2006/080302 A1 (U.S. Pat. No. 7,637,981) or Japanese Application No. 2009-142837 can be used as the composite material 20. The composite material 20 has a thickness of, for example, 2 to 3 mm.

The composite wear resistant member described in WO2006/080302 A1 (U.S. Pat. No. 7,637,981) contains hard particles including diamond particles and WC particles, and an iron group metal containing phosphorous and serving as a binding material. In this case, the amount of the phosphorous is 0.05 wt % to 1.0 wt % of the total weight of the WC particles and the binding material. A method for manufacturing the composite wear resistant member includes a step of adjusting a ratio of phosphorus with respect to a material comprising superhard and hard particles including diamond particles and WC particles and a binding material including a phosphorus (P)-containing iron group metal to set an proper sintering temperature to 900-1100° C.; and a step of performing hot-press sintering or spark plasma sintering.

Furthermore, the composite wear resistant member described in Japanese Application No. 2009-142837 is manufactured by a step of a setting an appropriate sintering temperature from 900° C. to 1080° C. by adjusting a ratio of phosphor in a material, wherein the material contains hard particles including diamond particles and WC particles, a binder of an iron group metal containing phosphor (P), and copper, which is distributed and is present alone; and

performing hot press sintering or electric discharge sintering on the material. Alternatively, the composite wear resistant member described in Japanese Application No. 2009-142837 is manufactured by a step of laying a copper layer on top of a base layer having hard particles including diamond particles and WC particles, and a binding material of an iron group metal containing phosphorous (P), and then performing hot press sintering or discharge sintering.

The thus manufactured composite wear resistant member described in Japanese Application No. 2009-142837 is a diamond composite material containing copper dispersed therein and used for bits. The diamond composite material can be used by being stacked on cemented carbide, iron group metal, or the like.

Alternatively, the composite wear resistant member described in Japanese Application No. 2009-142837 may be a diamond composite material in which a copper plate or net and a diamond composite material are stacked on each other. In the present invention, the diamond composite material can be used by being stacked on cemented carbide, iron group metal, or the like.

The cemented carbide tips (diamond tips) 12, 14, and 18 used for the conventional rock bit offer high wear resistance performance but no grinding capability.

The diamond composite tip (diamond composite material) 20 with diamond particles dispersed therein according to the present invention is characterized by offering high wear resistance performance and an excellent grinding capability.

The diamond composite material with diamond particles (or c-BN) dispersed therein is disposed on the gauge surface 16 and preferably disposed extensively and smoothly on the gauge surface 16. Then, this configuration is used to grind the well wall to release the pressure from the well wall applied to the bit. This significantly reduces loads imposed on the bearings 8 a and 8 b.

The diamond composite material can be disposed on a part of the bit body 4 and preferably disposed extensively and smoothly on a part of the bit body 4. In particular, the diamond composite material can be disposed and preferably disposed extensively and smoothly.

The diamond composite material can be disposed on a part of the gauge tip and preferably disposed extensively and smoothly on a part of the gauge tip.

Embodiment 2

Now, a rock bit according to another embodiment of the present invention will be described with reference to FIG. 9. Like the rock bit according to Embodiment 1, this tri-cone bit includes a bit body 4 with a journal portion 2, a cone portion 6 configured to be rotatable with respect to the bit body 4, and a bearing portion 8 located between the cone portion 6 and the journal portion 2. The bearing portion 8 includes a ball bearing 8 a and a metal bearing 8 b. The rock bit further includes a seal 10 provided between the cone portion 6 and the journal portion 2 to seal the bearing portion 8.

Unlike in the case of Embodiment 1, a ring portion 30 is provided at the outer peripheral portion of the bit body 4. A ring bit 32 is provided at the tip of the ring portion 30. Furthermore, the cone portion 6 of the tri-cone bit includes no gauge tip or gauge surface tip which contacts the side wall of the well but only cemented carbide tips 12 that contact the bottom of the well.

A diamond composite material (not shown in the drawings) is disposed on the ring bit 32 and preferably disposed extensively and smoothly on the ring bit 32.

The diamond composite material may be the one described in WO2006/080302 A1 (U.S. Pat. No. 7,637,981) or Japanese Application No. 2009-142837 and manufactured by the above-described manufacturing method. In particular, the diamond composite material described in Japanese Application No. 2009-142837 may be stacked on cemented carbide, iron group metal, or the like, and the stack may be disposed on the ring bit 32 and preferably disposed extensively and smoothly on the ring bit 32. The thickness of this composite material may be almost the same as that of the ring bit 32 (for example, 1 cm to 5 cm).

According to the rock bit of Embodiment 2, the ring bit 32 located at the tip of the cylindrical ring portion 30 is used to grind the outer peripheral portion of the digging pit. Then, the normal tri-cone bit located inside the ring portion 30 is used to dig the cylindrical rocks remaining in the central portion. This prevents pressure from the well wall from being applied to the gauge surface 16 of the tri-cone bit.

The outer peripheral portion of the bit rotates at high speed, and this meets a grinding condition for the ring bit. However, the central portion of the bit rotates at low speed. Thus, it is ideal to use a tri-cone bit to crush rocks during digging according to the conventional example. Furthermore, the cylindrical ring portion 30 prevents digging debris from entering the seal 10 and increases cooling efficiency to protect the seal 10 from high temperature such as geothermal heat.

Thus, it is also effective to shape the rock bit such that the ring bit 32 is disposed at the outer peripheral portion of the tri-cone bit so as to merge with the tri-cone bit (this rock bit is hereinafter referred to as a merged bit).

In this case, the tri-cone bit need not serve to maintain the digging diameter (the ring bit instead fulfils this function), and there is no need to worry about the wear of the gauge surface or the like.

Moreover, no parallel pressure or vibration is applied to the seal 10, allowing the ring portion 30 to rotate in the ideal environment.

It should be further understood by those skilled in the art that although the foregoing description has been made on embodiments of the invention, the invention is not limited thereto and various changes and modifications may be made without departing from the spirit of the invention and the scope of the appended claims. 

1. A rock bit comprising: a bit body with a journal portion; a cone portion configured to be rotatable with respect to the bit body; a bearing portion located between the cone portion and the journal portion; and a seal provided between the cone portion and the journal portion to seal the bearing portion, wherein the cone portion includes a gauge surface that contacts a side wall of a well, and a diamond composite material is disposed on the gauge surface.
 2. The rock bit according to claim 1, wherein the diamond composite material is disposed on the bit body.
 3. The rock bit according to claim 1, further comprising a gauge tip that contacts the side wall of the well, and the diamond composite material is disposed on a part of the gauge tip.
 4. The rock bit according to any one of claims 1 to 3, wherein the diamond composite material is disposed by being stacked on cemented carbide.
 5. The rock bit according to any one of claims 1 to 3, wherein the diamond composite material is disposed by being stacked, on iron group metal.
 6. A rock bit comprising: a tri-cone bit comprising: a bit body with a journal portion; a cone portion configured to be rotatable with respect to the bit body; a bearing portion located between the cone portion and the journal portion; and a seal provided between the cone portion and the journal portion to seal the bearing portion; and a cylindrical ring portion fixed to an outer periphery of the tri-cone bit and including a ring bit located at a tip of the ring portion so as to contact a side wall of a well.
 7. The rock bit according to claim 6, wherein the diamond composite material is disposed on the ring bit.
 8. The rock bit according to claim 6 or 7, wherein the diamond composite material is disposed by being stacked on cemented carbide.
 9. The rock bit according to claim 6 or 7, wherein the diamond composite material is disposed by being stacked on iron group metal. 